**4. Molecular genetic analysis**

Genotyping of the studied polymorphisms of the DRD4, DAT genes was performed in the Laboratory of Molecular Genetic Studies of Therapeutic Diseases Research Institute of Internal and Preventive Medicine - Branch of the Institute of Cytology and Genetics SB RAS, Novosibirsk, Russia. DNA preparation was conducted there as well. The phenol-chloroform extraction method was used [21, 22]. 5–6 volumes of buffer A (10 mM Tris–HCl, pH = 7.5; 10 mM NaCl; 3 mM MgCl2) were added to a blood sample (~ 10 ml) and hemodialysis was performed by grinding clots in a Potter homogenizer. The precipitates were obtained after centrifugation at 2500 g and washed twice with buffer A, then resuspended in 0.5 ml of buffer B (10 mM EDTA; 100 mM NaCl; 50 mM Tris–HCl, pH = 8.5). After adding SDS to 0.5% and proteinase K to 200 μg / ml, the mixture was incubated for 2 hours at 65° C, or overnight at 37° C. Deproteinization was carried out sequentially with water-saturated phenol, a mixture of phenol-chloroform (1: 1) and chloroform. DNA was precipitated by the addition of NH4Ac to 2.5 M and 2.5 V ethanol. The precipitate obtained by centrifugation in an Eppendorf microcentrifuge for 10 minutes was washed with 70% ethanol and dissolved DNA in water to a concentration of 0.5 μg / μl.
